The present invention relates generally to systems and devices utilizing lasers, and more specifically to a system for removing materials such as paint and other coatings from various surfaces, wherein the system includes a laser scanner having multiple cooperative optics having unique characteristics.
The application of laser technology for the removal of coatings developed several decades ago and small hand-held devices (100-500 W) are now available commercially for small area coating removal tasks. “Coating” typically refers to all types of unwanted surface material found on a substrate, including paint, rust, oil, grease, adhesives, sealant, barnacles, radioactive contamination, chemical agent contamination, and the like. Laser technology offers numerous advantages over conventional methods for removal of coatings (e.g., media blasting, chemical stripping, etc.), including no use of hazardous materials, no required inventory of expendable material, minimal preparation of the object to be processed, greater precision of coating removal, higher coating removal rates, and minimal post-process cleanup.
Options for large area coating removal with lasers are currently being developed. To meet the desired coating removal rates for large areas (such as large aircraft surfaces, ships, buildings, and bridges), laser power levels in the 5 to 10-kW range are suitable for applications involving paint coatings. The desired removal rates are in the range of about 1 to 3 ft2/min. The typical removal rate that can be achieved with currently available lasers is about 2 ft2/min (per 1 mil of coating thickness for each 1 kW of laser power delivered to the surface). This rate of removal presumes that the laser beam is delivered to the surface in an appropriate pattern and is scanned across the surface at rates that remove coating without alteration of the substrate when it is exposed.
For delicate or unstable substrates, such as 0.020-inch thick aluminum, the system for scanning a laser beam over the surface should achieve clean coating removal without causing thermal damage, charring, or otherwise altering the substrate. Some success has been achieved with galvanometer-based oscillatory scanning mirrors; however, these scans are limited in surface scan speed to typically less than 10 m/s and suffer from dead zones at the end of the scan where the mirror decelerates, reverses, and reaccelerates. These dead zones may be eliminated in practice with beam blockers that limit the scan width and lose average power at the work surface. Other limitations of currently available oscillatory scanners are power handling capability (<6 kW) and weight (>60 lbs). Due to the limitations of known systems, there an ongoing need for an advanced laser scanner system that will meet the requirements of certain industrial or governmental applications requiring laser power levels up to 10 kW.